The copolymers consist of organic segments A which cannot be crosslinked by a radical route or by a Diels Alder reaction, which are identical or different, each having a valency i such that 1 >= i >= 6 and identical or different segments Z(CH2)j in each of which Z denotes an organic radical which has a valency j such that 1 >= j >= 6, the radicals Z additionally containing at least one functional group permitting crosslinking by a radical route or by a Diels Alder reaction; each segment of one of the species being linked to at least one segment of the other species by an ether or primary or secondary amine functional group Y. They are obtained by polycondensation of monomers HYAYH and of monomers Z(CH2X)j, Y being a leaving group.